The four climbers — a German doctor, a Nepal-born Canadian citizen, a South Korean mountaineer, and a Chinese climber — died as a result of exhaustion and high-altitude sickness on their way down from the summit.

A major issue this year wreaking havoc on the health of Everest scalers is a phenomenon known as the "traffic jam."

A confluence of complications — late start to an already tight climbing season, a rise in the number of climbers looking to summit the mountain, and an overcrowding at the perilous "Hillary Step" leading to the top — has resulted in a life-threatening bottleneck that leaves climbers stranded at the summit for longer than is advisable.

"That's a hell of a lot of standing around," says experienced expeditionist Tom Briggs. "That certainly increases the dangers of frostbite and other problems like high-altitude sickness."